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Biomedical subjects

A Kappas

Publications and source records attributed to A Kappas.

At least 343 records · Page 19Linked to original sources
PubMed1970

Stimulation of mammalian erythropoiesis by 5beta-H steroid metabolites.

The effects of a number of steroid compounds on erythropoiesis in normal and polycythemic mice were examined. Of the steroids that stimulated erythropoiesis, the hormone testosterone and certain 5beta-H C(19) and C(21) nonhormonal metabolites were the most effective. Anti-erythropoietin abolished the erythropoiesis-stimulating effects of testosterone but not those exerted by the 5beta-H steroid, 11-ketopregnanolone. Similarly, testosterone but not 11-ketopregnanolone evoked the production of erythropoiesis-stimulating factor in rats. It is concluded that two mechanisms underlie the stimulating actions of steroids on erythropoiesis; one through the production of erythropoietin and the second involving a more direct influence on the blood-forming tissues. The 5beta-H steroid metabolites are postulated to act on erythropoiesis via the latter mechanism.

Animals↗
PubMed1969

The occurrence of substances in human plasma capable of inducing the enzyme delta-aminolevulinate synthetase in liver cells.

We have demonstrated the presence, in the plasma of several patients with acute intermittent porphyria, of a substance which strongly induced the synthesis of porphyrins in chick embryo liver cells growing in primary culture. The induction response evoked by this humoral agent was in all respects similar to that elicited by drugs and hormones which are known to enhance porphyrin production by inducing the de novo formation of delta-aminolevulinate synthetase, the rate-limiting enzyme in this pathway. Inducing properties were not found in the plasma of normal individuals or in that from porphyric patients in remission. Significant inducing activity was, however, found in the plasma of some normal subjects ingesting drugs or contraceptive steroid mixtures. The occurrence of a potent inducer of delta-aminolevulinate synthetase in the plasma of certain porphyric patients may have clinical significance for these genetically susceptible individuals. It will also permit chemical characterization of those humoral agents which may be related to the episodic exacerbations of this hereditary liver disease.

Animals↗
PubMed1969

Plasma membranes of the rat liver. Isolation and enzymatic characterization of a fraction rich in bile canaliculi.

A method is described for the rapid isolation of a plasma membrane fraction containing a high concentration of intact bile canaliculi from the rat liver. Isolated bile canaliculi retain most of the ultrastructural features exhibited in the intact liver cell. The final fraction contains 5'-nucleotidase activity at approximately the same concentration as that in previous preparations of plasma membranes. In the presence of 0.01 M Mg(++), 5'-nucleotidase exhibits a double pH optimum at pH values of 7.5 and 9.5. The activities of glucose-6-phosphatase and alkaline phosphatase are present in low amounts. Cytochrome P-450 is not detectable. Na(+)-K(+)-activation of ATPase is observed to the extent of 20-36% in about half of the assays. The availability of a method for preparation of intact bile canaliculi should prove useful for studying the biochemical events associated with the transport of bile constituents into canaliculi.

Adenosine Triphosphatases↗